Method of treating synthetic polymer latex of styrenebutadiene or polyisoprene to make solid polymer derived therefrom redispersible to a latex

ABSTRACT

A method of treating synthetic polyisoprene and styrene butadiene latices comprising adding to the latex particular redispersing agents so that the solid rubber obtained when the water is removed from the latex is redispersible. Various redispersing agents are described including urea and combinations of urea with supplementary agents. Reconstituted latices obtained from such redispersible solid rubbers have comparable properties with freshly prepared latices.

United States Patent 1 1 1111 3,904,567

Sung 1 1 Sept. 9, 1975 [54] INIETHOD ()F TREATING SYNTHETIC 193811178 12/1933 Iver 260/760 POLYMER LATEX 0F 2.653344 11/1953 Anderson 2610/23.?I 2,880,184 3/1959 Groves Ct :11 260/2917 STYRENEBUTADIENE 0R POLYISOEIRENE 2,961452 12/1960 Sinri Ct 211 i 260/297 TO MAKE 50L") POLYMER DERIVED 3,232,899 1/1966 Guziak..... 260/2911 PM THEREFROM REDISPERSIBLE TO A 3,288,741 11/1966 Chcng v. zoo/x51 LATEX 3,413,247 11/1968 Schroeder 260/17 [75] Inventor: Chin Pong Sung, Kuala Lumpur, OTHER PUBLICATIONS Malaysia Surface Active Agents and Detergents. Vol 11 [73] Assignee. Thc Board of the Rubber Research Schwartz et HI. pp 328M329 and 732%739 lnstltute of Malaysia, Malaysia {22] Filed: 1973 Primary Examiner-Melvin Goldstein [31 A N 390,246 Assistant ExaminerEdward Woodberry Armrney, Agent, or FirmWenderoth, Lind & Ponack [30] Foreign Application Priority Data Aug 17. 1973 United Kingdom 3851l/72 {57] ABSTRACT [52] us CL 7 H 260/217 R; 260/174 A method of treating synthetic polyisoprene and sty- 260/17 4 renc butadiene latices comprising adding to the latex [3] 1 lm CHM C08C 4/00, COM 5/00, CU8L 9/00. particular redispersing agents so that the solid rubber CU8L 91/06 obtained when the water is removed from the latex is I58] Field of Search l r I 260/174 BB 7A R redispersihlci Various redispersing agents are de- /I 7 4 SG 85 I 29 6 Q scribed including urea and combinations of urea with k 7 3 j supplementary agents. Reconstitutcd latices obtained 9 i from such redispersible solid rubbers have comparable [g6] Rderences Cied properties with freshly prepared latices. UNITED STATES PATENTS 10 Claims N0 Drawings LXZfyflIU ill/1931 Schradcr i i i 4 260/760 METHOD OF TREATING SYNTHETIC POLYMER LATEX OF STYRENEBUTADIENE OR POLYISOPRENE TO MAKE SOLID POLYMER DERIVED THEREFROM REDISPERSIBLE TO A LATEX The present invention relates to the preservation of synthetic rubber latex in the form of re-dispersible solids or low moisture content pastes.

Synthetic rubber in the form of its latex is an important material particularly in the production of soft and foamed rubber goods, the manufacture of which is frequently performed in places far removed from the source of the latex. The present invention is directed in part to the provision of latices in solid form which are particularly convenient for transport and for the preparation of for example foam materials on site.

Further the solid latices are believed to be useful in the manufacture of so called -flexible plasters."

The present invention provides a method of making a solid or pasty synthetic rubber which is dispersible in water. which method comprises providing a latex of the synthetic rubber in admixture with a re-dispersing agent. and removing water from the latex The invention also includes synthetic rubber in solid or paste form which contains a re-dispersing agent and is dispersible in water.

Whilst it is liclie cd that the invention is. in general. applicable to a wide range of synthetic rubbers. it has been found that it is particularly applicable to styrenebutadienc rubber [SBR] and polyisoprene rubber. Because of the slightly differing surface properties of the latex particles of these rubbers. there are some differences in the compounds found to be completely effective in these two types of synthetic latices. Among SBR latices those prepared by emulsion polymerisation (cg. lntex l()()) are preferred and among polyisoprene latices those prepared by solution polymerisation (eg. Cariflcx IR 7H0) are preferred.

While it will normally be preferred to use the minimum quantity of rc-dispersing agent necessary to confer adequate rc-dispersibility on the solid rubber, there is no reason in principle why greater amounts of redispersing agent should not be used. The maximum concentration of re-dispersing agent is thus not critical, and will generally be that at which other properties of the rubber start to significantly deteriorate.

Styrene ButadieneRubber By this term. we mean clastomcric copolymers of styrene and butadicne. which copolymers may optionally contain minor proportions of other monomers copolymeriscd therewith.

Preferred redispersing agents for styrenobutadiene rubber latices are urea. polyhydric alcohols and mono and di-saccharides. Generally. these rcdispersing agents are used in amounts of from 0.05% to 107/ by weight on the weight of the dry rubber. Amounts below [H phr may not be sufficient to achieve complete re-tlispersibility of the solid or pasty rubber. Little added advantage is gained by the use of amounts above 5.0 phrv Preferred polyhydric alcohols having at least 3 bydroxyl groups per molecule include glycerol. mannitol. sorbitol. quebrachitol and inositol. Pentaerythritol is less effective. Preferred saccharides include 11 glu cose, fructose. 11 galactose. L arabinosc. d arabinosc. sucrose, 1/ mannose and lactose.

In general, where mixtures are used there is no need to add supplementary agents over and above the fatty acid soap level normally used in the production of SBR latices. Attention is drawn to the publication entitled Description of Synthetic Rubbers and Latices" published by the International Institute of Synthetic Rub' ber Producers lnc.. 45 Rockefeller Plaza, New York, NY. I0020 1968 Jan edition, wherein it is noted that four types of emulsifying systems are used in the production of SBR latex. These are fatty acid, rosinacid, a mixture ofa fatty acid and a roxin-acid and salt acid. The experiments made so far have been using a SBR latex which contained a fatty acid soap emulsifying system. The results have indicated that the further addition of a rosin-acid soap to the SBR latex used in the experiments, interferes with the re-dispersibility of the rubber. This is illustrated in Example No. 7. It is accordingly preferred in the present invention to prepare the redispersible rubber of the invention from a latex substantially free from rosin-acids.

Polyisoprene Rubber By this term we mean an elastomeric polymer of polyisoprene. either cisor trans-polyisoprene or a mixture of the two, either a homopolymer or a co-polymer ofa major proportion of polyisoprene with a minor pro portion of another co-polymerisable monomer.

Preferred re-dispersing agents for polyisoprene rubber latices are either saponin alone, or a mixture of a. at least one compound selected from glycosides,

polyhydric alcohols, urea. and mono and disaccharides. with b. at least one alkali metal or ammonium salt of an organic acid having a C to C aliphatic carbon chain.

Generally. the re-dispersing agent is used in an amount of from 2 to 20 phr. Saponin is very effective alone in concentrations of the order of 10 phr. Where mixtures are used, each component is preferably present in an amount of at least 1 phr., and the mixture in an amount of at least 3 phr.

Examples of suitable glycosides are the saponins and digitonin. Preferred polyhydric alcohols in clude glycerol, mannitol, sorbitol. quebrachitol and inositol. Preferred saccharides include d glucose. fructose. d galactose, L arabinose. d arabinose. sucrose. d marmose. and lactose.

Among compounds of group b) above, there may be mentioned potassium palmitate; potassium oleate; the ammonium. sodium and potassium salts of capric, caprylic. lauric. stearic, ricinoleic and linoleic acids either by themselves or in various combinations as they would occur in natural vegetable oil soaps, e.g. coconut oil soap and castor oil soap; and the agent sold by lCl under the Trade Mark Vulcastab LS. believed to be so dium oleyl para-anisidine sulphonate.

The method used to dry the treated latex is not critical but in commercial operation the normal spray drying techniques are satisfactory. The specific examples use a laboratory method of drying the rubber as thin films on glass plates. The general technique used throughout the examples. unless otherwise specified. is as follows:

The retlispersing agent either in aqueous solution or dispersion. typically at about HM by weight. or as the free material. is added to portions of the synthetic rub ber latex and the mixture is thoroughly stirred. The mixture is spread onto glass plates and dried in air at 29C (ambient temperature) typically for from 48 to 54 hours. producing films about 2.5 mm. thickv The typi cal moisture content is from 0.8% to 2.0%. A typical average figure is l .89. The dried paste is removed from the glass plate with a spatula. The rubber is then redispersed in a minimum amount of water by high speed stirring in a commercial liquidiser for ca 31) seconds. The redispersibility can be quantitatively assessed by determining the quantity retained by seiving through fine muslin.

In the Examples, Examples l to 7 relate to SBR latex and Examples 8 to l0 polyisoprene latex.

The SBR latex used in the examples is a commercial type sold under the trade name lntex l()(). The polyisoprene latex is a commercial eis-l .4-polyisoprene latex sold under the trade name Cariflex IR 700.

EXAMPLE 1 Samples olstyrenebutadiene latex were treated with Parts by weight tlr Zinc oxide line tlieth ldithioearbamate Zinc mereaptobcivothia/ole Antioxidant Sulphur Foaming agent (potassium oleatel l'rinienc base Sodium silicolluoride Foams were made from unmatured latex and no filler was added. Vulcanisation was carried out at lUUC for 30 minutes and drying for [6 hours at 70C. The samples were tested according to the technique described in the appropriate British Standards specifications. The results are given below.

Re-dispersed SBR treated Re-dispe rsed 5BR treated ('ontrol with L5); wt. with 1' 5 wt SBR glycerol commercial brown sugar Density, D (gm em "1 [H14 H.105 (HUT Volume shrinkage '7r l4.2 15.5 I17 Compression modulus. C [gm cm Single flex 55.9 44.3 4'-J.| Initial 55.8 42.9 49.] Fgnigucd 54.24 41.4 47.6 Aged 22hr/7(l(. (17.!) 56.6 n.d. Fatigue loss 7r L8 3.5 2.9 Age hardening "/1 201) 32.0 n.d. C/D 2.5 Single flex I26 l2.5 ill) Initial l2! l2.l I31) Fatigucd l2.4 ll.7 12.7 Aged 22 hrl7llC l5.l lfill n.d. Compression set Static 72 hr/ZUT 2.2 3.4 l5 Static 22 hr/7()C 7.4 7.6 5.2 Dynamic l.] 1.5 l.] Tcnsile strength kg cm l),7(l (L64 0,59 Elongation at break "/1 2(15 l'lll l5 n.l.lv not determined (21) L571 by weight glycerol as a l()% aqueous solution and (b) 2% by weight commercial brown sugar, both percentages being by weight on the weight of the dry rubber. The reconstituted latices had the following properties:

Using the same technique further samples were prepared and the data thus obtained indicate that the addi tion of as much as 5% by weight glycerol or the commercial grade of brown sugar to SBR latex do not adversely affect the properties of the raw latex Treatment Dry Total pH Mechanical l3rook rubber solids stability field content '4 wt. time (sec) viscosity -l lcpsl SBR control (lntex llll) or HIS) (wh,l4 (18.72 9.60 ltltltl 765 Re-dispcrsed 5BR treated with 1.50! wt, glycerol e510 68.82 ll),ll(l Zllllll 745 Re dispersetl SBR treated with 2% t. commercial brovtn sugar (13.44 65.5) 9 )ll Zlltltl 4Z0 Electron micrographs of these reconstituted latices EXAMPLE 2 show no observable differences between the reconsti- 6c.

tuted and control.

The latices were compounded using the following formulations:

This lnample illustrates the effect of adding urea. at \arious concentrations, on the redispersibility of SBR latex at various concentrations. on the rcdispersihility of Cnncen Cuagulum SBR Lu[e\;

traitiun Appearance on addition of WZIICF content phr to dry ruhhcr wt Control Film was coherent. llil) ll. Film was partially coherent. S4 m,

Mlllfmcis nmcd l mmmmtrution Appearance on addition of water content Partially TC'LlISPCI'QthlC phr m dr) mhhcr w (1.3 Film was completely non-coherent; 4

immediate milkiness on addition of water Control Film was coherent Hll) (t7 1 Film was completely flOllC0hcTL'l1t; (I 10 l 'f l f immediate milkiness on addition of P lulu water, particles. Partial rcl (I 1 Completely redispersihle. (I dispcrsihility ot'thc rubber was evident. 0,4 1 Film was completely nun-coherent. (I Milky dispersion of later particles. As in Example l a sample of styrcne-butadienc latex 5 Us Complete redispcrsihilily 0 was treated with 3% by wt. of urea. The reconstituted latex had the following preperties:

Similar results were obtained with lactose.

Total Mechanical EXAMPLE 5 1 rcutnient Solids pH stability '4 wt. time (set!) This Example illustrates the effect of adding Glyc- SBR mm (8 x7 3000 em], at various concentrations, on the redispersibility Rc-dispersetl SBR treated 67.91) 9.55 2000 t SBR Latex h .W l The effectiveness of glycerol in redispcrsmg SBR is evident from the above results. Glycerol mono-oleate. Th l i were compounded to h f l i d mono-ricinoleate and mono-stearate were also experiscribed in Example 1 and the properties of the foam m n d at Concentrations between 3 l0 phr. but the rubber are shown below effects on redispersibility were not similar to that of Re-dispersed SBR Control treated with SBR 3'7? wt. urea Density. D lgm. cm 0.!25 (J. l l7 Volume shrinkage '7? l2 9 14.) Compression modulus. C (gm. cm

Single flex 79,6 64.7 Initial 80.3 66.2 Fatigucd 77.7 64.3 Fatigue loss 'kl 3.3 2.) (ID Single flex 145 ll? initial l4.6 l4.l Faitigucd l4.l l3.6 Compression set Static 72 hr, 2()(' 2.2 3.0 Dynamic l l L] EXAMPLE 3 glycerol. Large flocs of rubber particles were observed and re-dispersion was incomplete even at such high This Example illustrates the effect of adding Glucose,

concentrations. Glycerol diacetate was also found to be at various concentrations, on the redispersibility of SBR Latex ineffective even at concentrations of 2 l0 phr.

Coagulum Concentration Appearance on addition of water content phr to dry rubber wt. Concen- Cougulurn tration Appearance on addition of water content Control Film was coherent IOU phr to dry rubber "/r wt.

U2 Films were completely non- U 4 h r n u ry milky 0 0 Film was coherent ion dispersion of late 0 (1.2 Films were completely non- 0 particles- ()4 coherent. Immediate milkincss (l (1.8 on addition of water, (1

Similar results were obtained with the following monosaccharides: fructose. d-mannose, d-galactose, l- EXAMPLE 6 arabinose and d-arabinose.

, This Example illustrates the effect of adding Manni- EXAMPLE to]. at various concentrations, on the redispersibility of This Example illustrates the effect of adding Sucrose, SBR Latex.

Concelr (oagulum tration Appearance on addition of water content phr on dry rubber (l wt.

(1 Film was coherent lt)(l (L2 Film was mainly non-coherentv 2 lmmcdiate milkiness on addition of water. Almost complete rc dispersibility. 0.4 l Films were completely non coherent. ll

Immediate milkiness on addition of 0.8 water Complete re'dispersibility. ll

Similar results were obtained with sorbitol, mesoinositol and quebrachitol.

EXAMPLE 7 acid soup to a treated SBR latex interferes with the re dispersibility of the rubber. Potassium palmitate inter fercs. to a lesser extent, with the redispersibility of the rubber as illustrated in the following table.

('oagulum content r2 wt.

Addition ol' potassium Rcdispersibilit pillnllltiltf tphrl it I] ltli) l) llli) l ltll) EXAMPLES 8 TO l0 Using the method described above the effectiveness of various redispersing agents on Cariflex IR 700 latex.

The supplier of Cariflex IR 700 has stated that a po tassium soap of rosin-acid was used in the production of this latex. Rosin-acid is sometimes described as a monocarboxylic acid of an alkylated hydrophenanthrene nuclei". The type used in Cariflex lR 700 is the abietic acid type. Approximately 2 percent of this soap is present in Cariflex IR 700. This figure has been confirmed by analysis.

Table Component (a) Component 1h) Appearance on addition (oagulum content of water to dry rubber 9% wt.

Control rubber Nil Film was coherent ltltl Nil Example 3. Effect of saponin It) phr saponin Nil Film was completely non U coherent Milky dispersion of latex particles. 8 phr saponin 5 phr Vulca' do. t)

stab 1.5. U phr saponin 5 phr Vulca- Film was coherent. ll)(l stab.

Example 9. Effect of mono-saecharide 3 phr glucose 5 phr potass- Film was completely non- (l ium oleate coherent. Milky dispersion of latex particles Nil 5 phr potass- Film coherent. ltltl ium oleatc 2 phr glucose Nil do. IUU

Example lt). Effect of polyhydric alcohol 2 phr glycerol 3 phr potass- Film was completely non ium oleate coherent Milk dispersion of latex particles. 2 phr glycerol nil Film coherent ltll) I claim:

(oagulum content Re-dispcrsihility 1-,

Addition olpotassium rosin-acid soap llll) ltlll II (I Hi U 1 ll loo 2 13 3o 24 To All Inn in 51) loo o It is clear that the addition of 2 phr of potassium rosin 3. A method as claimed in claim 1 wherein the proportion of re-dispersing agent is from Ovl to by weight on the weight of the dry rubber.

4. A solid or pasty styrene butadiene rubber which is dispersible in water and comprises styrene butadiene rubber mixture with at least 0.05% by weight urea as a re-dispersing agent.

5. A method of making a solid or pasty synthetic polyisoprcne rubber which is dispersible in water, which method comprises adding a. at least 1% by weight of urea, and

h. at least 171. by weight of at least one alkali metal or ammonium salt of an organic carboxylic or sulphonic acid having a C7 to C30 aliphatic carbon chain. as a re-dispersing agent, to a synthetic polyisoprene rubber latex and, removing water from the latex.

6. A method as claimed in claim 5, wherein the polyisoprenc is prepared by solution polymerisation.

7. A method as claimed in claim 5, wherein the sum fill of urea and the alkali metal or ammonium salt of the organic acid is from 2 to 20% by weight on the weight of the dry rubber 8. A solid or pasty polyisoprene rubber which is dispersiblc in water and comprises polyisoprene rubber in admixture with (a) at least 1% by weight of area (b) at least 1% by weight ofat least I alkali metal or ammonium salt of an organic carboxylic or sulphonic acid having a C7 to C30 aliphatic carbon chain, as a redispersing agent.

9. A method as claimed in claim 5, wherein the salt of the organic acid is sodium oleyl para-anisidine sulphonate.

10. A method as claimed in claim 5, wherein the salt of the organic acid is selected from the group consisting of potassium palmitate, potassium olelate, and the am' monium, sodium, and potassium salts of capric, caprylic, lauric, stearic ricinoleic linoleic acids and mixtures thereof. 

1. A METHOD OF MAKING A SOLID OR PASTY SYNTHETIC STYRENEBUTADIENE RUBBER WHICH IS DISPERIBLE IN WATER, WHICH METHOD COMPRISES ADDING AT LEAST 0.05% BY WEIGHT OF UREA, AS A RE-DIS PERSING AGENT, TO A STYRENE-BUTADIENE RUBBER LATEX AND REMOVING WATER FROM THE LATEX
 2. A method as claimed in claim 1, wherein the styrene butadiene rubber is made by an emulsion polymerisation process.
 3. A method as claimed in claim 1 wherein the proportion of re-dispersing agent is from 0.1 to 10% by weight on the weight of the dry rubber.
 4. A solid or pasty styrene butadiene rubber which is dispersible in water and comprises styrene butadiene rubber mixture with at least 0.05% by weight urea as a re-dispersing agent.
 5. A method of making a solid or pasty synthetic polyisoprene rubber which is dispersible in water, which method comprises adding a. at least 1% by weight of urea, and b. at least 1% by weight of at least one alkali metal or ammonium salt of an organic carboxylic or sulphonic acid having a C7 to C30 aliphatic carbon chain, as a re-dispersing agent, to a synthetic polyisoprene rubber latex and, removing water from the latex.
 6. A method as claimed in claim 5, wherein the polyisoprene is prepared by solution polymerisation.
 7. A method as claimed in claim 5, wherein the sum of urea and the alkali metal or ammonium salt of the organic acid is from 2 to 20% by weight on the weight of the dry rubber.
 8. A solid or pasty polyisoprene rubber which is dispersible in water and comprises polyisoprene rubber in admixture with (a) at least 1% by weight of urea, (b) at least 1% by weight of at least 1 alkali metal or ammonium salt of an organic carboxylic or sulphonic acid having a C7 to C30 aliphatic carbon chain, as a re-dispersing agent.
 9. A method as claimed in claim 5, wherein the salt of the organic acid is sodium oleyl para-anisidine sulphonate.
 10. A method as claimed in claim 5, wherein the salt of the organic acid is selected from the group consisting of potassium palmitate, potassium olelate, and the ammonium, sodium, and potassium salts of capric, caprylic, lauric, stearic, ricinoleic linoleic acids and mixtures thereof. 